Priority is claimed with respect to European Patent Application No. 98810207.5-2302 filed in the European Patent Office on Mar. 11, 1998, the disclosure of which is incorporated herein by reference.
The invention relates to a cutting machine for automatically trimming printed products such as brochures, magazines, and catalogues transported spine first to first and second cutting stations spaced from one another in the transport direction. Each station includes at least one clamping bar for clamping the printed product during a trimming operation and at least one blade associated with the clamping bar that is movable up and down for trimming at least one of the front, top, and bottom of the printed products, wherein the blades of the cutting stations are movable together. In such a machine, transport means are provided for transporting the printed products along a conveying path from the first cutting station to the second cutting station, and adjustable stops are associated with the cutting stations and disposed along the conveying path for the printed products.
Cutting machines of this type have long been known, and are used, among other things, for producing brochures, magazines or books following gathering and stapling, or other binding processes.
A known cutting machine produced by Grapha Holding AG, the assignee of the invention disclosed herein, is embodied as a so-called three-side trimmer. At a first cutting station, the front is trimmed transversely to the conveying direction of the printed products, that is, the edge of the open side is trimmed to size. In the second cutting station, the top and bottom of the printed product are cut with two oppositely-located blades. A cut through the center can be made in addition to the top and bottom cuts. In one cutting stroke of the blades, two printed products are trimmed, one at the front and the other at the top and bottom. If there is an additional center cut, it is simpler to trim the front before the top and bottom because of the guides. Each cutting station has stops, and a transport device having upper and lower belts is provided between the cutting stations of the cutting machine.
Similar cutting machines are disclosed in CH-A-340479 and CH-A-531401.
One essential requirement for such cutting machines is the highest-possible production speed or production output. This is especially a function of the format and thickness of a printed product, or the weight of the printed product and the quality of the paper. Thin, stable printed products can be moved at high speeds. Thick, heavy and voluminous printed products must be processed at reduced speeds. The attainable production speeds are strongly influenced by the width of the printed products seen in the transport direction, the distance between the two cutting stations and the length of the conveying path between the stations, respectively. The front edge, or the open side, of the printed products is cut by a blade of a cutting station, the blade being disposed transversely to the transport direction, while, in contrast, the top and bottom edges are simultaneously trimmed by two oppositely-located blades of the next cutting station, the blades being oriented in the transport direction of the printed products.
The respectively more stable binding or spine of a printed product constitutes the reference edge, according to which the front is trimmed with specific spacing. In other words, the printed products are transported, with their spine or binding forward, toward the stops associated with the corresponding cutting station. It must be kept in mind here that the blades specified for trimming the top and bottom must not make an undesired cut in, or otherwise damage, the preceding or following printed product.
It is an object of the invention to provide a cutting machine of the aforementioned generic type that permits the optimization of the production speed with respect to format.
This object is accomplished in the context of the generic cutting machine first described above, wherein the conveying path of the transport means formed by the spacing between stops associated with the cutting stations, and the cutting region specified for top and bottom trimming along the conveying path of the printed products, are variable.
Consequently, in the cutting machine of the invention, it is possible to alternate between at least two format ranges, and the distance between two cutting stations can be optimally adapted to the current printed-product format.
In contrast to the known cutting machines, in which the cutting stations are spaced at fixed intervals, in the cutting machine of the invention, the distance between the cutting stations can be, for example, reduced, for a given printed product. Such a reduction permits a corresponding increase in the speed of the printed products.
The format adaptation additionally permits an optimization of the delay and acceleration of the printed products between the cutting stations. Difficult-to-process printed products, for example, very thin, sensitive and slick printed products, can be optimally accelerated and delayed. Moreover, the cutting machine offers careful handling of the products.
The invention is explained below with reference to the drawings. All details not discussed at length in the description are to be inferred from the drawings.